US20220252431A1 - Determination of axial and rotary position of a body - Google Patents

Determination of axial and rotary position of a body Download PDF

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Publication number
US20220252431A1
US20220252431A1 US17/625,238 US202017625238A US2022252431A1 US 20220252431 A1 US20220252431 A1 US 20220252431A1 US 202017625238 A US202017625238 A US 202017625238A US 2022252431 A1 US2022252431 A1 US 2022252431A1
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detection
excitation
magnetic field
longitudinal axis
coils
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Philipp Bühler
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Mecos AG
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Mecos AG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/204—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils
    • G01D5/2073—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils by movement of a single coil with respect to two or more coils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/22—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils
    • G01D5/2208—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils by influencing the self-induction of the coils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/30—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring angles or tapers; for testing the alignment of axes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/142—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/142—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices
    • G01D5/145—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices influenced by the relative movement between the Hall device and magnetic fields
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/16—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying resistance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/204—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils
    • G01D5/2053—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils by a movable non-ferromagnetic conductive element
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/22—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils

Definitions

  • the present invention relates to a sensor device for determining at least one of the axial and rotary positions of a body, and to a corresponding method.
  • WO 2004/048883 A1 discloses a sensor device for determining the position of a body along multiple degrees of freedom.
  • An excitation coil extends around an electrically conductive body.
  • a plurality of pickup coils or other magnetic field sensors are placed in the vicinity of the excitation coil at different angular positions along the circumference of the body.
  • a high-frequency current is fed to the excitation coil, thus generating a high-frequency magnetic field.
  • Eddy currents are generated in the conductive body as a result of the high-frequency magnetic field.
  • the eddy currents prevent the high-frequency magnetic field from entering the bulk of the body.
  • the magnetic field lines are therefore concentrated in the gap between the excitation coil and the body. Movements of the body will change the magnetic field distribution. These changes are picked up by the pickup coils.
  • the magnetic field distribution When the body moves in one direction so as to decrease the size of the gap on one side of the body, the magnetic field distribution will essentially move in the opposite direction, such that a pickup coil on the side where the gap size increases will receive a larger signal. If the average gap size between the excitation coil and the body is small compared to its diameter, the movement of the magnetic field distribution can be much larger than the movement of the body. This leads to high sensitivity of the device.
  • WO 2004/048883 A1 further suggests determining the axial position of a rotationally symmetric body along its symmetry axis by providing an annular axial flange surface on the body, the surface normal of the flange surface extending along the symmetry axis of the body, and arranging the excitation coil and/or pickup coils axially opposite the flange surface (see FIGS. 7 and 8 of WO 2004/048883 A1).
  • the size of the axial gap between the flange surface and the coils is evaluated by determining the sum of the signals of all the pickup coils that are distributed around the body, or by evaluating the impedance of the excitation coil.
  • WO 2006/074560 A2 discloses an axial position sensor that comprises at least two coplanar, concentric sensor coils.
  • the sensor coils are arranged around the rotation axis of a thrust disk, axially facing the thrust disk. They are operated such that magnetic fields generated by the sensor coils cancel at least partially in the regions inside the innermost sensor coil and outside the outmost sensor coil.
  • several pickup coils are provided in the vicinity of the sensor coils or of a separate excitation coil. The pickup coils detect a rotary position of a notch that is provided on the thrust disk or on a shaft that carries the thrust disk.
  • the axial position sensor disclosed in WO 2004/048883 A1 has the same disadvantages as the axial position sensor disclosed in WO 2004/048883 A1 in that it requires the coils to axially face a target. Furthermore, concerning the determination of rotary position, the sensor requires a notch near the pickup coils, which can interfere with the determination of the axial position.
  • a sensor device for determining an axial position of a body along a longitudinal axis comprising:
  • the sensor device comprises one first detection coil and one second detection coil, both detection coils extending around the longitudinal axis.
  • This embodiment is particularly suitable if it is desired to only determine the axial position of the body.
  • the sensor device comprises a plurality of first detection coils arranged essentially in the first detection plane at a plurality of different angular positions around the longitudinal axis (i.e., at different angular positions along the circumference of the excitation coil), and a plurality of second detection coils arranged essentially in the second detection plane perpendicular to the longitudinal axis at a plurality of different angular positions around the longitudinal axis.
  • each of the first and second detection coils preferably does not extend around the longitudinal axis.
  • the first and second detection coils can be arranged to form pairs of axially opposing first and second detection coils.
  • the first detection coil and the second detection coil of each pair are preferably congruent in a projection along the longitudinal axis.
  • the determination of the axial position can then be based on a sum over all differences between signals from each pair of axially opposing first and second detection coils, or, equivalently, on the difference between the sum of the signals from all first detection coils and the sum of the signals from all second detection coils.
  • the sums and differences can be formed by the wiring scheme, i.e., by connecting the coils in series and anti-series configuration such that the desired sums and differences are obtained, by analog hardware (e.g., by analog adders and subtractors), by digital hard- and software (e.g. by digitizing the signals from the detection coils and adding and subtracting them in software), or by a combination of these possibilities.
  • analog hardware e.g., by analog adders and subtractors
  • digital hard- and software e.g. by digitizing the signals from the detection coils and adding and subtracting them in software
  • the sensor device further comprises a plurality of third detection coils arranged in the vicinity of the excitation coil at a plurality of different angular positions around the longitudinal axis. These additional detection coils can then be used to determine the position of the body along at least one degree of freedom different from the axial direction instead of or in addition to the first and second detection coils.
  • the detection circuitry is configured to determine, in addition to the axial position of the body, a radial position of the body along at least one radial direction. Such a determination may be based on at least one sum of the signals that are detected by the first detection coils and the signals that are detected by the second detection coils. In particular, sums may be formed for the signals from each pair of axially opposing first and second detection coils, and linear combinations may be formed of such sums for pairs that are arranged at different angular positions around the longitudinal axis (i.e., along the circumference of the body or, equivalently, along the circumference of the excitation coil). In other embodiments, the determination of radial position may be based on signals from the third detection coils. Also in this case, linear combinations may be formed of the signals from third detection coils at different angular positions along the circumference of the body.
  • the detection circuitry is configured to determine, in addition to the axial position of the body, a tilt position of the body (in particular, of its longitudinal axis relative to the detection planes) around at least one radial tilt axis. Such a determination may be based on a comparison of at least two differences between signals that are detected by the first detection coils and signals that are detected by the second detection coils, each difference being formed from signals for a different angular position around the longitudinal axis.
  • the excitation coil is preferably arranged in a symmetric manner with respect to the detection planes. In particular, it can be arranged between the detection planes. In some embodiments, the excitation coil is arranged essentially in an excitation plane, the excitation plane being arranged between the first and second detection planes and preferably equidistantly from the first and second detection planes. In such embodiments, the excitation and detection coils can radially overlap in a projection along the longitudinal direction. In other embodiments, the excitation coil comprises first and second windings, the first winding being arranged essentially in the first detection plane, and the second winding being arranged essentially in the second detection plane. In such embodiments, it is preferred that the first detection coils are arranged radially outside the first winding, and the second detection coils are arranged radially outside the second winding. Other relative arrangements of the excitation and detection coils are of course possible as well.
  • the sensor device is advantageously used in conjunction with an electrically conductive target on the body that has, on its outer circumference, at least one radial dimension that varies along the longitudinal axis.
  • the excitation coil extends around the circumference of the target, i.e., the target is arranged radially inside the excitation coil.
  • the excitation coil is arranged sufficiently close to the target that the excitation magnetic field distribution excites eddy currents in the target.
  • the eddy currents prevent the excitation magnetic field distribution from entering the bulk of the target (except for a thin zone at the surface having a thickness on the scale of the so-called skin depth). Axial movements of the target will therefore change the magnetic field distribution around the target.
  • the magnetic field distribution is detected by the detection coils. By forming differences between signals from detection coils in two different, axially spaced detection planes, a very sensitive measure of axial position can be obtained.
  • the excitation coil and the detection coils do not radially overlap with the target or at least not with those portions of the target in which the eddy currents are excited.
  • the target does not comprise an axial flange surface that axially faces the excitation and/or detection coils. In this manner the relevant portion of the target can easily be inserted into the arrangement of coils and removed therefrom without collision.
  • This does not exclude, of course, that there are other structures on the body that do radially overlap with the coils, for instance, a thrust disk for axial magnetic bearings. What is important is only that these structures do not form the target for the present sensor device, i.e., they are not involved in the measurement process by the sensor device.
  • the excitation frequency should be comparatively high in order to minimize the skin depth up to which the magnetic field distribution can enter the target and in order to avoid interference from other currents, e.g., control currents.
  • the excitation frequency is at least 100 kHz.
  • the excitation frequency is at least 200 kHz, at least 500 kHz, at least 1 MHz or even at least 2 MHz.
  • the excitation frequency should not be too high in order to avoid waveguide effects as with microwaves.
  • the excitation frequency may be chosen to be not more than 100 MHz. In some embodiments, the excitation frequency is not more than 20 MHz or not more than 10 MHz.
  • a permanent magnet 11 having a north pole N and a south pole S is mounted on the rotor body 10 for interaction with stator windings (not shown) on the stator.
  • the stator windings and the permanent magnet 11 together form an electric motor or generator.
  • the direction of magnetization of the permanent magnet 11 is transverse to the rotation axis A.
  • the printed circuit board 25 also carries an excitation coil.
  • the excitation coil is disposed in one or more central layers of the printed circuit board 25 between the first and second detection planes and is not visible in FIG. 1 .
  • the excitation coil extends around the rotor body 10 , i.e., its turns encircle the rotation axis A.
  • the target ring 12 has a length L along the rotational direction A that essentially corresponds to the distance D between the first and second detection planes P 1 , P 2 along the Z direction.
  • the target ring 12 has two oppositely oriented circumferential edge structures: A first (upper) circumferential edge 15 is present where the outer circumferential surface of the target ring 12 meets the upper axial end face of the target ring 12 .
  • a second (lower) circumferential edge 16 is present where the outer circumferential surface of the target ring 12 meets the lower axial end face of the target ring 12 .
  • the current creates a high-frequency excitation magnetic field distribution.
  • the magnetic field distribution excites eddy currents in the target ring.
  • the eddy currents prevent the magnetic field distribution from entering the bulk of the target ring. This leads to a concentration of the magnetic field distribution in the radial gap 13 between the excitation coil 23 and the circumferential surface of the target ring 12 .
  • Radial displacements of the rotor body 10 along some radial direction decrease the gap size on one radial side and increase the gap size on the opposite radial side of the target ring 12 . This leads to a displacement of the magnetic field distribution in a direction opposite to the direction of movement of the target ring 12 .
  • the first and second detection coils 21 , 22 on the one radial side receive a smaller signal than the first and second detection coils 21 , 22 on the other radial side.
  • the radial displacement can be determined based on this difference.
  • FIG. 3 illustrates a second embodiment.
  • the excitation coil 23 has two windings 231 , 232 .
  • the first winding 231 is disposed in the first detection plane P 1 , radially inside of the first detection coils 21 .
  • the second winding 232 is disposed in the second detection plane P 2 , radially inside of the second detection coils 22 .
  • the windings 231 , 232 have the same numbers of turns. They are connected in series.
  • FIG. 4 illustrates a third embodiment.
  • the excitation and detection coils are arranged as in the first embodiment.
  • a notch 14 is provided in the rotor body 10 .
  • the portion of the rotor body 10 that is near the notch 14 forms the target for the excitation and detection coils.
  • the magnetic field distribution will be concentrated in the notch 14 .
  • the magnetic field distribution will move together with the rotor body. This again will lead to different signals in the first and second detection coils 21 , 22 .
  • third detection coils 26 can be used for detecting radial displacements, while the first and second detection coils 21 , 22 are used only for detecting axial displacements and possibly tilt displacements. This may simplify signal processing.
  • each pair of first and second detection coils 21 , 22 may be directly connected in an anti-series configuration to directly obtain a difference signal from each pair without the need of electronics for forming such differences.
  • first detection coils 21 distributed along the circumference of the excitation coil 23 and corresponding second detection coils 22
  • second detection coils 22 each of these coils extending around the longitudinal axis A (or, equivalently, around the body 10 ).
  • These two coils may be connected in an anti-series configuration to directly obtain a difference signal from these coils.
  • the axial position of the body 10 can be determined in this manner in a particularly simple manner.
  • third detection coils 26 arranged at different positions along the circumference of the excitation coil can be provided for determining radial displacements of the body.
  • the excitation and detection coils are possible.
  • many other configurations of the target are possible.
  • the target does not necessarily need to have sharp edge structures.
  • the signals received from each pair of first and second detection coils are subtracted. This results in four difference signals ⁇ a, ⁇ b, ⁇ c, and ⁇ d, one difference signal for each pair.
  • the magnetic field sensors 24 are operated independently of the excitation and detection coils. These sensors detect the stray magnetic field from the magnet 11 of the motor or generator. In the example of FIG. 5 , four magnetic field sensor signals are obtained. The signals from each pair of diametrically opposed magnetic field sensors may be subtracted to minimize the influence of radial displacements of the rotor body 10 . This results in two difference signals along two mutually orthogonal directions, from which the rotary position of the rotor body 10 can be readily determined using methods well known in the art.
  • FIG. 6 illustrates a fourth embodiment, in which only three first detection coils 21 , three second detection coils 22 (not visible in FIG. 6 ) and three magnetic field sensors 24 are provided. Again, sums and differences of the signals from each pair of first and second detection coils 21 , 22 are formed. By forming appropriately weighted linear combinations of these sums and differences, it is readily possible to again determine radial, axial and tilt displacements of the rotor body in the same spirit as explained in conjunction with FIG. 5 . By forming linear combinations of the signals of the three magnetic field sensors, signals along two mutually orthogonal directions are obtained. The rotary position of the rotor body 10 can be readily determined from these signals.
  • the signals from the magnetic field sensors will be influenced by radial displacements of the rotor body 10 , and the influence cannot be compensated by forming linear combinations any more. However, this influence can still be corrected based on the radial displacement signals obtained from the detection coils 21 , 22 and/or 26 .
  • FIG. 7 illustrates a possible embodiment of the processing circuitry 30 .
  • the processing circuitry comprises excitation circuitry 31 and detection circuitry 32 .
  • the excitation circuitry 31 comprises an oscillator that supplies a high-frequency current to the excitation coil 23 at the excitation frequency. Voltages are induced in first and second detection coils 21 , 22 .
  • the detection circuitry comprises a subtractor 33 that subtracts the voltage signals received from the first and second detection coils 21 , 22 from one another, followed by a bandpass filter 34 having a center frequency at the excitation frequency to filter out any undesired disturbances.
  • the output from the bandpass filter is fed to a demodulator/ADC 35 that demodulates the high-frequency signal to obtain a low-frequency signal that is a measure of the amplitude of the output from subtractor 33 at the excitation frequency.
  • This signal is digitized and outputted.
  • the output is indicative of an axial displacement of a target portion near the pair of detection coils 21 , 22 .
  • an adder 36 adds the voltage signals received from the first and second detection coils 21 , 22 .
  • the output from the adder is again passed through a bandpass filter 37 and demodulated and digitized in a demodulator/ADC 38 .
  • the output is indicative of a radial position of a target portion near the pair of detection coils 21 , 22 .
  • FIG. 7 Only one pair of detection coils with the corresponding processing circuitry is shown in FIG. 7 .
  • the processing circuitry for the other pairs of detections coils is identical.
  • the outputs of the processing circuitry for the different pairs of detection coils can then be combined and subjected to further treatment in software.
  • FIG. 7 is provided only by way of example, and that the excitation and detection circuitry can be configured in many different manners.
  • the signal from each detection coil can be processed and digitized separately, and all further processing can be carried out fully digitally.
  • further sums and differences can be formed by analog hardware before digitization of the signals.
  • the detection coils can even be hardwired in a configuration that directly provides the desired sums or differences.

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EP19187014.6A EP3767242B1 (en) 2019-07-18 2019-07-18 Determination of axial and rotary positions of a body
PCT/EP2020/068944 WO2021008914A1 (en) 2019-07-18 2020-07-06 Determination of axial and rotary positions of a body

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CN114158272B (zh) 2024-02-02
WO2021008914A1 (en) 2021-01-21

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